Buick made 2122 "KX" code dual quad 425, high compression, 360 hp 465 ft lb "Super Wildcat" Rivieras, about 800 Wildcats, and at least 1 Electra, a four door, in 1964 (the Wildcats had stick shifts, did the Rivs or Electras?)

https://www.uniqueclassiccars.com/vehicles/1314/1964-buick-riviera-425-360hp-dual-quad

The Electra is analyzed at https://forums.aaca.org/topic/321875-1964-dual-quad-electra-production-numbers/

In 1964, there were 26 convertible Wildcats with the Hurst 4 speed https://www.v8buick.com/index.php?threads/1964-super-wildcat-4-sp-dual-quad-convertible-62-500.345148/

https://www.hemmings.com/stories/article/unconventionally-muscular-1964-buick-wildcat

In 1965, Buick only made 617 dual quad 425s

1965 Dual Quad Production Numbers 

617 for all series 8000 (1965)

 14   8237 (2 Door)

 13   8239 (4-Door Hardtop) 

16    8269 (4-Door Sedan) 

91    8437 (2-Door Custom)

314  8439 (4-Door Custom Hardtop)

123  8467 Convertibles 

46    8469 (4-door Custom Sedan)

from Daily Car Report, Buick Motor Division, 08-24-65, pp 230-269